how to add markers at limits of fplot matlab? - matlab

Question

I want to add markers at the limits of a function in matlab. I am plotting the function using fplot this is what I tried:
user_func = '2*x-3';
user_limits = '-2,2';
user_limits = regexp(user_limits, '\,', 'split');
user_limit(1) = str2num(user_limits{1});
user_limit(2) = str2num(user_limits{2});
h = fplot(func,limits);
I am trying to add markers at the limits only (size 10 color 'r'). any idea on how to do that?
thank you

Answer 1

Not sure if this is exactly what you are trying to accomplish but I modified your code slightly so I could plot the function (using an anonymous function):
user_func = #(x) 2*x-3;
user_limits = '-2,2';
user_limits = regexp(user_limits, '\,', 'split')
user_limit(1) = str2num(user_limits{1})
user_limit(2) = str2num(user_limits{2})
figure;fplot(user_func,[user_limit(1) user_limit(2)]);
Next, set the ticks at your locations and change the font size to 10 pt:
set(gca,'XTick',[user_limit(1) user_limit(2)],'FontSize',10);
Change the color of your labels to red:
set(gca, 'XColor', [1 0 0]);
set(gca, 'YColor', [1 0 0]);
Just so you can see the ticks, stretch the x-range a bit:
axis([-2.1 2.1 0 1]); axis 'auto y'
EDIT: After some additional input from the OP, the red tick markers can be plotted as shown below.
First let the x-position at the first limit be given by:
x1 = user_limit(1);
The y-value for first marker is then obtained from the anonymous function like this:
y1 = user_func(x1);
y2 = y1;
We have, y2 = y1, since you want the y-value where where your function first crosses the x-axis to be the same. Now make your plot like this (with x2 = user_limit(2)):
hold on;
plot(x1, y1, 'ro', x2, y2,'ro');
hold off;
giving a plot like: